1. Field of the Invention
The instant invention is directed to a catalyst useful in the polymerization of olefins. More particularly, the instant invention is directed to a catalyst, useful in the polymerization of olefins, wherein magnesium, vanadium and titanium compounds are disposed on an inert support.
2. Background of the Prior Art
The polymerization of olefins using Ziegler-Natta catalysts is almost universally employed. These catalysts provide polyolefins having desired characteristics in high yield. However, because of the myriad applications to which polyolefins are used, no single class of catalyst provides polymers having the specific desired utility.
A characteristic, however, common to many olefin polymerization catalysts in the prior art is the incorporation therein of internal electron donors. These compounds are utilized in applications which require high isotacticity. The presence of internal electron donors, however, creates difficulties in the use of the catalyst and the product produced. Those skilled in the art are aware that unless the amount and type of electron donor compound is carefully selected not only is stereoregularity of the resultant polymer deficient but poor catalytic activity often results. This detrimental effect occurs even if the catalyst is formed with the proper electron donor compound in the correct concentration added in the wrong sequence.
The utilization of electron donor compounds often create additional problems involving offensive odors in the final polymeric product. This unfortunate result obtains even if the ideal electron donor, provided in the correct concentration and introduced in proper sequence in the catalyst formation process, is utilized. Thus, polymers formed from catalysts which include an electron donor compound must oftentimes be deashed or deodorized in order to insure that there is no odor given off by the final polymeric product.
Another disadvantage identified in the prior art is the use of magnesium halide supports. Such supports are commonly utilized in the polymerization of propylene. This important class of olefins is oftentimes polymerized by a magnesium halide supported catalyst because of the advantageous results noted with such catalysts. Unfortunately, the use of such a support has adverse effects.
These adverse effects are partially ascribable to the corrosive nature of this compound. Molding machines which process polymers formed from polymerizations catalyzed by magnesium halide supported catalysts are subject to corrosion due to the corrosive nature of the polymer which includes magnesium halide supported catalyst therein. Moreover, the adverse effect of this corrosion is not limited to damage to expensive molding machinery. Equally significant, the polyolefinic molded article processed by this molding machinery is in many cases characterized by aesthetic flaws.
Very recently, a patent application assigned to the assignee of the present application was developed which addressed the issues discussed above. That is, a new catalyst was developed which produces olefinic polymers, particularly propylene polymers, of high stereoregularity, uniform particle size distribution, good spherical morphology and high bulk density. Although this invention, embodied in U.S. patent application, Ser. No. 326,708, filed Mar. 21, 1989, which is a continuation of U.S. patent application, Ser. No. 99,190, filed Sept. 21, 1988, now abandoned, also represents an advance in the art in terms of olefinic polymer productivity, that catalyst does not produce a polymer that can rapidly be processed in such applications as injection molded applications to produce products in the high rate required for commercialization.
The above remarks establish that there is a continuing need in the art for catalysts useful in the polymerization of olefins that not only eliminate the problems associated with corrosive supports and the formation of catalysts utilizing internal electron donors but, in addition, produce olefinic polymers having melt indeces or melt flow rates such that injected molded products can be produced in high yield.